In a superconducting linear accelerator that accelerates protons or heavy ions, sometimes a quarter wave resonator (QWR) or a half wave resonator (HWR) is used to form an acceleration cavity. Microwaves are input into the acceleration cavity to generate an accelerating field that accelerates the protons or heavy ions. At this time, the particles can be accelerated efficiently by synchronizing the natural resonance frequency of the acceleration cavity with the frequency of the accelerating field. Accordingly, the acceleration cavity needs to be tuned to adjust the resonance frequency of the acceleration cavity.
Patent Literatures 1 and 2 below disclose inventions related to tuning of an acceleration cavity.